Hi I'm 5'11 65kgs (145pounds) and started kiting and surfing (without a kite) about a 6 months ago. The waves in my area only average 3-5 foot and I've been using an old 5'10 short board that recently broke...

I want to buy a decent surfboard that i can use for normal surfing (no kite) and also take kite surfing (when the conditions are easy enough)... What board size and width should i be looking at and what is a good compromise? Any things I need to avoid?

Kite surf boards seem to be quite wide and heavy what effect will this have for normal surfing?

If I got a specific kite surfboard (strapless) and used it in normal surfing (no kite) in 4-5 foot how would it perform?

Would a better balance be a kite surfboard for normal surfing or a normal surfboard for kiting?

it really depends on the actual board and your ability when it comes to surfing. I use the same boards for both although for me the 5'11 FW is a bit small for me to paddle at 6'2 and 85kg. the 6'3 Resin8 is my go to board for double overhead on the kite and overhead barrels surfing. this is a surfboard with no strap inserts!
for your size the 5'11 FW will surf fine as long as the waves are decent as the board has quite a bit of rocker, its the Taj pro model but with extra reinforcement and strap inserts. unless you are of pro level surf ability you will not notice any difference in feel to the standard Taj Firewire 5'11.
if your waves are a bit fatter then the new 5'8 dominator would be the go especially if you ride in lightish winds with the kite but if ride mostly with 7 or smaller then the 5'11 is sweet!